Wing scales. False-colour scanning electron micro- graph (SEM) of the wing of the common European Swallowtail butterfly Papilio machaon, showing its arrangement of wing scales. The structure of the wing is like a roof, with coloured scales corresponding to the overlapping tiles. The scales are attached to the wing membrane by a short stalk, which fits into a tubular socket. The colour of the butterfly's wing is determined by pigmentation of the scales and also by diffraction of light off the surface of each scale. The common European Swallowtail is coloured yellow and black, with stripes of blue and a red spot on the hind- wing. Magnification: x150 at 6x4.5cm size.